A fairly wide variety of pulverizing mowers exists in the prior art. See, for example, U.S. Pat. No. 4,318,268 to Szymanis on Mar. 9, 1982; U.S. Pat. No. 3,959,954 to Halsten on Jun. 1, 1976; U.S. Pat. No. 4,196,568 to Perry on Apr. 8, 1980; U.S. Pat. No. 3,531,923 to De Lay on Oct. 6, 1970; U.S. Pat. No. 4,189,903 to Jackson et al. on Feb. 26, 1980; and U.S. Pat. No. Re. 29,139 to Messner on Feb. 22, 1977.
Such pulverizing or mulching mowers differ from other cutting mowers in that the garden cuttings are pulverized into a fine mulch and redeposited on the ground, as opposed to being collected in a container for subsequent disposal. Two important measurements of the effectiveness and desirability of such mowers are first, how uniformly the resulting mulch is distributed on the ground, and second, how finely the cuttings are ground. These two factors both have an effect on how visibly noticeable the resulting mulch is after the lawn has been mowed.
Many of these devices include a first stage cutting blade and a second stage "batter" that essentially bashes the cuttings of the cutting blade into smaller particles. However, it has been found that providing a second stage blade with shear cutting action reduces the time required to obtain a smaller average mulch particle size. Further, many of these prior art devices direct their resulting lawn cuttings through an exhaust port located on either side of the device. As such, these types of devices tend to cause the mulch to collect in large, visually discernible piles.
Generally with such prior art devices, if one desires to have a very finely cut mulch one must slow the speed at which the device progresses over a given area of the lawn. Alternatively, if a coarser cut is desired, such as is acceptable for some coarse grass types, such devices may be pushed over the lawn relatively quickly. Therefore, adjusting the speed at which such devices travels over the lawn is proportional to the average particle size of the resulting mulch. This is true because, generally speaking, lawn cuttings travel through such devices once and are expelled; they have a greater chance of being picked-up again and subsequently cut to a smaller size if the mower is still in the area. Regulating the resulting size of the mulch in this manner is difficult at best. Users of such devices must frequently change the speed at which they are moving these types of mowers over the ground, such as at the edge of the lawn, when turning, when stopping for a moment to remove rocks or other objects from the mowing path, and the like. As a result, these types of prior art mowers often result in a non-uniform distribution of mulch and mulch size.
Clearly, then, there is a need for a mulching type mowing apparatus that distributes cuttings in a completely uniform, symmetric distribution. Such a needed device would also be more effective at pulverizing the lawn cuttings, and would provide a means for adjusting the average mulch particle size. The present invention fulfills these needs and provides further related advantages.